Characterization of initial events in bacterial surface colonization by two Pseudomonas species using image analysis

Abstract

The processes leading to bacterial colonization on solid-water interfaces are adsorption, desorption, growth, and erosion. These processes have been measured individually in situ in a flowing system in real time using image analysis. Four different substrata (copper, silicon, 316 stainless-steel and glass) and 2 different bacterial species (Pseudomonas aeruginosa and Pseudomonas fluorescens) were used in the experiments. The flow was laminar (Re = 1.4) and the shear stress was kept constant during all experiments at 0.75 N m(-2). The surface roughness varied among the substrata from 0.002 microm (for silicon) to 0.015 microm (for copper). Surface free energies varied from 25.1 dynes cm(-1) for silicon to 31.2 dynes cm(-1) for copper. Cell curface hydrophobicity, reported as hydrocarbon partitioning values, ranged from 0.67 for Ps. fluorescens to 0.97 for Ps. aeruginosa.The adsorption rate coefficient varied by as much as a factor of 10 among the combinations of bacterial strain and substratum material, and was positively correlated with surface free energy, the surface roughness of the substratum, and the hydrophobicity of the cells. The probability of desorption decreased with increasing surface free energy and surface roughness of the substratum. Cell growth was inhibited on copper, but replication of cells overlying an initial cell layer was observed with increased exposure time to the cell-containing bulk water. A mathematical model describing cell accumulation on a substratum is presented.

Microbial Adhesion in Flow Displacement Systems

“…After attachment of the colonizing bacteria, growth of the sessile population occurs. Although there is a reasonable amount of research done on all the steps in biofilm formation (66), a great deal of current interest resides in understanding the manner in which reversibly adhered bacteria make the transition to irreversible adhesion. Using GFP-labeled P. aeruginosa (76), the growth characteristics of planktonic bacteria and the initially adhering and secondary biofilm bacteria have been compared in a parallel plate flow chamber.…”

Effects of Substratum Topography on Bacterial Adhesion

“…This agrees with the results of Korber et al (17) where the same strains showed a two to three times enhanced attachment with motility. There are two common theories concerning the role of the flagella: (i) the ability to cross the energy barrier between the cell and the substratum to facilitate adhesion (22,34) and (ii) an effective increase in the cell diffusivity through the boundary layer fluid (24,28). It is possible that the lack of flagellar motion in the nonmotile strain (17) influenced the ability to cross the energy barrier, but it is more likely that the increased effective diffusivity of the motile strain resulted in more cell-surface collisions (23).…”

“…The ability of a bacterium suspended in fluid to cross the boundary and diffusion layers and reach the surface is influenced by sedimentation, attractive interactive forces, and a velocity component toward the surface provided by collisions between flowing particles (38). Diffusion is a critical component of cell-surface interaction and can be influenced by cell motility which can act to increase the effective diffusivity of the cells to the surface by up to four orders of magnitude (24,25). Piette and Idziak (28) have shown that Pseudomonas fluorescens flagellated cells attached in greater numbers than deflagellated cells.…”

Recent Advances in the Study of Microbiologically Influenced Corrosion

“…Muellar et al 1401 were able to determine rate coefficients for early bacterial colonization on copper, silicon, stainless steel and glass using a chemostat, a flow cell and a microscope equipped with an image analysis system. Reflective substrata were monitored using reflective light from a microscope equipped with a Nomarski lens and microscope output was linked to a video camera.…”